1. Technical Field
The present disclosure generally relates to a structure of an antenna array, and more particularly to an electromagnetic conductor reflecting plate, an antenna array using the electromagnetic conductor reflecting plate, and a radar and a communication apparatus using the antenna array.
2. Related Art
Along with the development of the communication technology, the antenna is seen in the usual life. To focus the energy of the antenna, the antenna array having the reflector is generally designed in the communication apparatus, such that the gain of the antenna is improved. However, the trend of the communication apparatus of every kind is toward to the slim and small size, and therefore the required size of the antenna is becoming smaller. Under the condition that the microminiaturized antenna with the high gain must be used, since the reflecting plate is generally confined in a limited space, the energy of the reflecting wave can not be focused fully and completely, and the antenna gain is thus decreased.
In addition to the communication apparatus, the radar generally adapts the large reflector, such as the parabolic reflector having the perfect electronic conductor (hereinafter abbreviated as “PEC”) or the artificial magnetic conductor (hereinafter abbreviated as “AMC”), such that the antenna gain is increased. Unfortunately, the size of the above reflector is large, and thus the manufacturing cost thereof is higher.
When the antenna adapts the PEC reflector, the tangent electric field at the boundary is zero, and the distance between the antenna and the PEC reflector is the odd multiple of the one-fourth wavelength of the radiated wave, but not zero, such that a set of the mirror currents having the same current phase is induced, and the phase of the reflected wave is identical to the phase of the incident wave. Although the manner can increase the energy of the reflected wave, it can not efficiently increase the antenna gain. In other words, regarding the antenna array having the PEC reflector as the reflecting plate, the distance between the antenna and the PEC reflector can not be too close, or the antenna gain is much decreased owing to the interference between the incident wave and the reflected wave.
Furthermore, another conventional antenna arrays adapting the perfect magnetic conductor (hereinafter abbreviated as PMC) reflecting plates are provided by U.S. Pat. No. 6,774,867, U.S. Pat. No. 6,853,350, and U.S. Pat. No. 7,463,213. In U.S. Pat. No. 6,853,350, the antenna is placed in the magnetic interface, and a radial current having the phase identical to that of the radiated wave is generated, such that the antenna reflection is improved. In U.S. Pat. No. 7,463,213, the antenna is placed in the PMC having the periodical high impedance, such that the antenna directivity is improved.
Regarding the antenna array using the PEC reflecting plate, the distance between the antenna and the PEC reflecting plate is the odd multiple of the one-fourth wavelength of the radiated wave, but not zero, and thus the position of the antenna can not be too close to the PEC reflecting plate. On the contrary, regarding the antenna array using the PMC reflecting plate, the distance between the antenna and the PMC reflecting plate is the multiple of the half wavelength of the radiated wave or zero, and thus the position of the antenna must be close to the PMC reflecting plate as far as possible.